Biexcitonic gain characteristics in ZnSe-based lasers with binary wells

We present systematic spectroscopic studies of the biexcitonic gain and its transition to electron-hole-plasma gain in ZnSe separate-confinement-heter ostructure lasers depending on well width, i.e., biexciton binding energy, excitation density, and temperature. The optical gain curves were obtained by means of the variable-stripe-length method under quasistationary conditi ons. The low-temperature gain spectra are modeled in the framework of a gas of excitons and biexcitons in chemical equilibrium. Sample-dependent redsh ifts of the gain curves are discussed and compared to the biexcitonic photo luminescence. At elevated temperatures (70-90 K), a steep increase of the l aser threshold density accompanied by a strong broadening of the gain curve s indicates a change of the gain process towards recombination of a strongl y Coulomb-correlated electron-hole-plasma. [S0163-1829(99)08631-2].